An original experimental setup has been designed that allows evaluation of the free preference of space containing tobacco smoke by small laboratory animals. For the laboratory mice (C57B1/6 and BALB/c) and rats (MNRA and MR) placed every day into this box, no emotional-stress reaction (ESR) caused by the environment novelty was observed on the 19th day of experiment. A difference in the free preference of space containing tobacco smoke was observed between inbred animals with active and passive ESR phenotypes.